1. Field of the Invention
This invention relates, in general, to ski apparatus and, more specifically, to ski bindings for releasably binding ski boots to skis.
2. Description of the Prior Art
Ski bindings are designed to detachably hold a skier's boots to his ski so as to provide sufficient control of the skis; while at the same time, releasing the boot from the ski when the external forces acting upon the ski exceed a threshold value to protect the skier from serious injury.
A popular type of ski binding is the so-called "step-in" type binding in which the toe of the boot engages a pivotable toe binding assembly and the heel of the boot is releasably latched in a heel binding unit. The toe binding assembly is held against rotation by a spring-loaded mechanism which provides an adjustable force to resist rotation of the toe binding due to external forces exerted on the bindings. The toe binding assembly rotates thereby releasing the boot from the binding when the threshold force level is exceeded, which threshold force level is adjustable by changing the compression of the spring.
It has been established that, during skiing, two significant forces act upon the binding to release the boot therefrom. These forces include the external leg forces involved in directing the ski downhill which act through the boot on the binding. The other force is the internal acceleration force resulting from the acceleration of the boot mass in either the horizontal or vertical direction. Since these two forces are additive, premature release of a binding during aggressive skiing can frequently occur without a fall or the skier being in danger of injury due to the large acceleration forces acting upon the bindings. Thus, it is common to increase the spring compression in order to prevent premature binding release caused by the internal acceleration forces. However, when the skier goes through a slow, twisting-type of fall, the acceleration forces are not present and the binding tension is set too high for the leg forces alone to cause a release of the boot from the binding before the skier's leg is fractured.
Recently, a new type of ski binding has been developed which completely eliminates the internal acceleration forces acting upon the ski binding. U.S. Pat. No. 4,129,245 discloses an acceleration compensated ski boot retaining device which comprises a pivot member adapted to engage a portion of the ski boot. The pivot member is pivotally carried such that the ski boot engaging portion of the pivot member pivots on one side of the pivot plane. The device further comprises a mass having means connecting the mass to the pivot member such that the center of gravity of the mass is on the other side of the pivot plane. The mass is sized to generate a moment at the pivot plane which is equal to and opposite to the moment generated by the boot mass during lateral and/or vertical accelerations of the boot to thereby cancel out the internal acceleration forces acting against the binding.
In order for such a ski binding to function properly, it is necessary that fulcrum distance between the contact point of the boot and the pivot point of the toe binding assembly remains constant. It has been found in step-in bindings that the boot can engage the toe-cup assembly in a variety of different locations so as to make the fulcrum length between the effective acting point of the boot mass and the binding pivot point dependent upon the actual boot position. This uncertainty impairs the proper functioning of the acceleration compensated ski binding release device since the moments on each side of the pivot point would no longer be balanced.
Thus, it would be desirable to provide an acceleration compensated ski binding release device which is suitable for use with step-in type bindings. It would also be desirable to provide an acceleration compensated ski binding release device whose proper operation is not dependent upon the point that the ski boot actually engages the toe-cup assembly of the ski binding. Also it would be desirable to provide an acceleration compensated ski binding release device in which the fulcrum length between the contact point of the boot mass and the pivot point of the binding remains constant regardless of where the boot actually engages the toe-cup assembly of the binding.